The Strongest Sage with the Weakest Crest

To learn magic, 12 years old nobleman Matthias takes the examination to enter the Royal Academy. He effortlessly deals with a monster on his way. To help other candidates, Lurie and Alma, he uses unorthodox enchantment spells and shows them his destructive power. Despite bearing the "Crest of Failure", Matthias is powerful. Who exactly is he?

In fact, Matthias is the reincarnation of the sage, Gaius, from several thousand years ago! He easily defeats his opponent in the inter-school competition. However, his opponent is actually a Demon who should have been eliminated in his previous life. The Demons go on the aggressive. To defeat the Demons, Matthias ventures into a dungeon with Lurie and Alma.

Two Demons appear in the city. Matthias cannot fight both at once so he tackles one while Lurie and Alma take on the other. The situation turns grim as the Demon has the upper hand against Matthias. Lurie and Alma also lack experience. Matthias unleashes his power as the previous sage. Meanwhile, a powerful friend appears...

Matthias is already friends with Iris, the Dark Dragon, in his previous life. Riding on her back, they visit the village where Demons hide. Although the Demons are surprised by Matthias's ambush, they already have a plan. Matthias then returns to the capital city and proposes something ridiculous to Iris.

A horde of monsters is attacking the capital. To protect the city, Matthias plans to erect a barrier. He seeks help from the First Academy and collects materials in the dungeon. However, the First Academy has its fighting spirit stoked. Its principal refuses to help and even summons a dragon in the dungeon by mistake. Just one surprise after another...

The Demons appear around the capital. Matthias is busy erecting the barrier so he sends Lurie and Alma to fend off the Demons. Without letting Matthias down, they defeat the Demons effortlessly. However, the Demons call upon their last resort. They gather at the capital. The battle between the academy students and the Demons is imminent.

Matthias leaves the academy and heads to the city dungeon, Melkia, to investigate the Dracopulse Lines. However, he discovers that Melkia is largely abandoned due to tyranny and the swarms of powerful monsters. To investigate this mysterious dungeon, Matthias and his party need to procure a permit from the Adventurer's Guild. They encounter another monster's attack...

Matthias, who is almost captured by the cruel lord's assassins, retaliates. He even obtains the king's permission and plans to arrest the city lord. Ambushing from his manor's entrance, Matthias and Eik, the king's messenger, captures the city lord. Seeing the city lord's unusual behavior, Matthias can't help but suspect the Demons, who have their eyes on the dungeon.

After defeating the Demons in the dungeon, Matthias is intercepted by the head demon. To find out its identity, Matthias wants to use the tracking device his previous self invented. He then heads to Radinia Alliance. However, to enter the territory equipped with the device, he has to become an A-rank adventurer. The adventurer, Giaas, and the rank-up test examiner present themselves.

Now A-rank adventurers, Matthias and his party head to Folkia where the tracking device is located. However, Folkia is ruled by Demons! They use magic to manipulate humans and are building a weapon of mass destruction in secret. Matthias and others cannot let this carry on and they use Iris's potent magical power to do the unexpected...

Giaas defeats the head demon to find out that it's a corpse puppeteered by powerful magic. Matthias is certain that whoever controls the corpse is the mastermind of everything. They enter ancient ruins that house a magical civilization. However, everything found inside the ruins is made by Matthias in his previous life...

The highest-ranking Demon, Zardias, has been revived. Even Matthias is powerless against his overwhelming strength. Alma and Lurie plan to return to the kingdom's weaponry to retrieve the sword forged by Matthias in his previous life. However, the Demons take the academy students hostage to impede their progress. Can Matthias overcome this unprecedented crisis?